The present invention is directed to a wrapper for a smoking article and particularly an inner wrap for a smoking article to reduce spotting.
In the manufacturing of smoking articles, and particularly cigarettes, in the last few years there has been a considerable amount of detail paid to the wrappers for use in encasing a tobacco rod or other smokeable materials. There has been considerable concern for the reduction of secondary or sidestream smoke which is a by-product of the combustion of a smoking article as well as selected additives to reduce fire propensity which are formulated into the cigarette wrapper. Moreover, there have been suggestions of circumscribing tobacco rods with a plurality of wrappers wherein each wrapper has certain additives therein to reduce this sidestream smoke as well as fire propensity. However, in many cases the types of additives that have been added to the cigarette wrapping papers have created off-taste or reduced the smoke quality or created undesirable appearances in the smoking article.
For example, U.S. Pat. No. 4,225,636 and U.S. Pat. No. 4,505,282 teach taste improvement in a smoking article by using a carbon inner liner in a smoking article. And, U.S. Pat. No. 5,172,708 teaches an improvement in the yellow spotting or staining with a double wrap cigarette paper wherein the inner wrap is comprised of a mixture of wood fibers, specifically pine and birch.
Spotting of the exterior wrapper on cigarettes occurs over time by either the tobacco pigment and/or flavor/casing additives transferring to the exterior layer of paper. Spotting is accelerated by transportation/storage temperatures above 90xc2x0 F. and high humidity. Temperatures of 120-130xc2x0 F. have been recorded during product transit from manufacturer to the final end market, especially during summer months.
It is an object of the present invention to provide a wrapper that eliminates spotting of the exterior paper wrapper during transportation/storage of the smoking article.
It is another object of the present invention to provide a double wrap smoking article wherein the inner wrap improves the taste quality of the smoking article and simultaneously reduces spotting or staining.
It is a further object of the present invention to provide an inner wrap for a smoking article wherein the inner wrap includes at least 50% by weight of wood fibers and less than 50% by weight of flax. Preferably, wood fibers would make up from 55 to 85% by weight of the inner wrap fiber matrix with the remainder being flax. It has been found that in manufacturing an inner wrap for the spotting/staining via a double wrap smoking article that the lower the basis weight of the paper and the higher the porosity was desirable. For example, inner wrap papers having a basis weight of less than 15 gm/M2 decreases irritation from smoke as the basis weight is lowered. Moreover, inner wrap papers having a basis weight of 12 gm/M2 demonstrated a lower irritation than an inner wrap having a basis weight of 15 gm/M2. And, inner wraps of a mixture of wood and flax where the fiber ratio was approximately 30% flax and 70% wood have been found to be better tasting with less smoke irritation in comparison with inner wraps comprised of a mixture of 50% abaca and 50% wood.
Double wrapped cigarettes using two conventional papers, made with flax or wood, or a combination of both fibers, having normal burn additives (0.3-2.5% citrates and 20-30% chalk), and normal porosity (10-120 Coresta) have been used in some products marketed in the past and are to some extent, still practiced today. The problem with using two layers of conventional papers is two-fold. First, the taste is negatively affected, by an increase in irritation, dryness, and overall papery character; and secondly, the smoke chemistry is changed by a substantial Increase in mainstream vapor phase smoke components.
One of the unique characteristics of the inner wrap of the present invention is that it is made to have a porosity that would be normally associated with porous filter plug wraps (5,000 to 160,000 Coresta). The advantage of using a high porosity inner wrap is that much of the vapor phase components in the mainstream smoke are not elevated.
In the preparation of smoking articles of the present invention, a double-wrap paper wrapper is wrapped around a tobacco rod wherein the outer wrap is a paper wrap which includes either 100% of flax fiber or 100% wood fiber or a mix of flax and wood fibers along with other-additives, such as calcium carbonate, and is at a basis weight of about 20-25 gm/M2 with a porosity in the neighborhood of 25-50 Coresta units with other additives which may include burn additives, and the like. The inner wrap is made up of from 55 to 85% percent, by weight, of wood fibers which includes soft wood, such as pine, and hard woods such as eucalyptus. Moreover, the inner wrap includes from about 15 to 45% by weight of flax. Preferably, the wood fiber is about 70% by weight and the flax is about 30% by weight. Generally, the flax is selected from the group consisting of bast flax fiber and shive flax fiber wherein the bast flax fiber is from 50 to 90% and the shive flax fibers is from 10 to 50%. Also, the inner wrap has a preferred basis weight of from 12 to 15 gm/M2 and a porosity of from about 200 to 160,000 Coresta units. The two wrappers then circumscribe a tobacco rod wherein the tobacco rod may be prepared from burley, flue cured, oriental, reconstituted tobacco, stems, or any combination in order to obtain a smokable product.